The present invention relates to semiconductor fabrication techniques and, more particularly, to methods of fabricating phase change materials and devices including the same.
Semiconductor memory devices may be classified into volatile memory devices, such as dynamic random access memory (DRAM) and static random access memory (SRAM), which typically cannot maintain data when a power supply is interrupted, and nonvolatile memory devices, such as flash memory and electrically erasable programmable read only memory (EEPROM), which can maintain data even when a power supply is interrupted. Flash memory is commonly used in electronic devices, such as memory cards or MP3 players, because of its nonvolatile characteristic.
Recently, next generation memory devices have been developed as potentially replacements for conventional flash memory. These next generation devices include magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM) and phase-change random access memory (FRAM). In a typical phase-change memory device, a chalcogen compound, such as germanium(Ge)-antimony(Sb)-tellurium(Te) (GST), is used as a phase-change material. Data is stored as a logic “0” or a logic “1” using a difference of a resistance caused by a reversible phase transition of the phase-change material. In particular, a composition ratio of a phase-change material or a composition distribution according to a thickness of a phase-change material may affect the resistivity of a phase-change layer, thereby determining an electrical characteristic of a phase-change memory device.